A vital sensing technique of estimating biological information of a person is expected to be applied not only to, for example, a home medical field or a health management field, but also to various fields such as detection of drowsiness during driving, acquisition of a mental state of a user during gaming, and detection of an abnormal person in a monitoring system. At present, most types of apparatuses sensing biological information are used to come into contact with a person's body, and a user is required to attach an apparatus thereto. Therefore, an application range thereof is restricted.
Thus, as one of countermeasures for sensing in a noncontact manner, there has been proposed a technique of estimating a pulse rate as an example of biological information on the basis of an image obtained through imaging in a camera. By using this technique, biological information can be sensed without a user's awareness, and thus it can be expected to enlarge an application range. For example, it is possible to detect a suspicious person whose pulse change increases due to stress while imaging with a monitoring camera. The technique also has a great advantage in that a plurality of people imaged by a single camera can be sensed together. When compared with a contact type, an individual apparatus is not required to be provided for each user, and it is also possible to reduce troublesomeness of attaching an apparatus to a body.
Here, regarding the related art of observing (monitoring) a biological state of a person, for example, there is a biological state observation system disclosed in PTL 1. In the biological state observation system, an image including at least one person to be observed, formed of a plurality of time-variant continuous frames, is input; a predetermined region in the image is detected, and information regarding the detected predetermined region is output; the biological information of the person to be observed included in the image is detected from the predetermined region in the image; and a predetermined biological parameter used for determining the abnormality of the biological state is compared with biological information data or a change in the biological information data so that the abnormality occurring in the biological state of the person to be observed is detected. Consequently, the biological state observation system can observe biological information of the person to be observed and detect the abnormality of the biological state of the person to be observed without giving discomfort and unpleasantness to the person to be observed. In PTL 1, the biological parameter used for comparison has a predetermined fixed value or a value which is updated via the Internet, and, when biological information of a person to be observed is observed, an abnormal person to be observed (a subject or a biological information processing target) is determined by using the value of the biological parameter.
As the related art regarding a pulse estimation technique using a camera, for example, there is a pulse measurement device disclosed in PTL 2. The pulse measurement device calculates a feature amount of a captured input image, detects a peak interval of a pulse wave on the basis of the calculated feature amount, and calculates a pulse rate on the basis of the detected peak interval of the pulse wave. The pulse measurement device controls a frame rate indicating the number of frames captured per unit time so that an estimated maximum error between a pulse rate having a valid peak interval based on an adoption proportion indicating a proportion of the valid peak interval in the calculated pulse rate and a true pulse rate is equal to or less than a prescribed value.